1. Field of the Invention
The present invention relates to backlight units. The present invention relates to display devices including the backlight units. The present invention relates to electronic devices provided with the display devices including the backlight units.
2. Description of the Related Art
Display devices typified by liquid crystal display devices are widely used in large display devices such as television receivers to small display devices such as cellular phones. High-value-added products will be needed and are being developed. In recent years, in view of rising interest in the global environment and improvement in convenience of mobile devices, development of low-power-consumption display devices has attracted attention.
As a low-power-consumption display device, there is a display device for displaying images by a field-sequential method (also referred to as a color-sequential display method, a time-division display method, or a successive additive color mixture display method). In the field-sequential method, lighting of backlights of red (hereinafter abbreviated to R in some cases), green (hereinafter abbreviated to G in some cases), and blue (hereinafter abbreviated to B in some cases) is switched with time, lights of R, G, and B are supplied to a display panel, and color images are viewed by additive color mixture. Thus, it is not necessary to provide a color filter in each pixel, the use efficiency of transmitting light from a backlight can be improved, and power consumption can be reduced. Since R, G, and B can be expressed in one pixel in a field-sequential display device, the field-sequential display device has an advantage that high-resolution images can be easily displayed.
Field-sequential drive has a unique display defect such as color breakup (also referred to as color break). It is known that the increase in frequency of write of video signals in a given period can reduce the problem of color breakup.
Patent Document 1 and Non-Patent Document 1 each disclose the structure of a field-sequential liquid crystal display device in which a display region is divided into a plurality of regions and a corresponding backlight unit is also divided into a plurality of regions in order to increase the frequency of write of video signals in a given period.